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SubjectRe: [PATCH] spi: spi-mtk-nor: fix timeout calculation overflow
On Tue, Sep 22, 2020 at 7:43 PM Chuanhong Guo <gch981213@gmail.com> wrote:
>
> CLK_TO_US macro is used to calculate potential transfer time for various
> timeout handling. However it overflows on transfer bigger than 512 bytes
> because it first did (len * 8 * 1000000).
> This controller typically operates at 45MHz. This patch did 2 things:
> 1. calculate clock / 1000000 first
> 2. add a 4M transfer size cap so that the final timeout in DMA reading
> doesn't overflow
>
> Fixes: 881d1ee9fe81f ("spi: add support for mediatek spi-nor controller")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
> ---
> drivers/spi/spi-mtk-nor.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
> index 6e6ca2b8e6c82..619313db42c0e 100644
> --- a/drivers/spi/spi-mtk-nor.c
> +++ b/drivers/spi/spi-mtk-nor.c
> @@ -89,7 +89,7 @@
> // Buffered page program can do one 128-byte transfer
> #define MTK_NOR_PP_SIZE 128
>
> -#define CLK_TO_US(sp, clkcnt) ((clkcnt) * 1000000 / sp->spi_freq)
> +#define CLK_TO_US(sp, clkcnt) DIV_ROUND_UP(clkcnt, sp->spi_freq / 1000000)
>
> struct mtk_nor {
> struct spi_controller *ctlr;
> @@ -177,6 +177,10 @@ static int mtk_nor_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
> if ((op->addr.nbytes == 3) || (op->addr.nbytes == 4)) {
> if ((op->data.dir == SPI_MEM_DATA_IN) &&
> mtk_nor_match_read(op)) {
> + // limit size to prevent timeout calculation overflow
> + if (op->data.nbytes > 0x2000000)
> + op->data.nbytes = 0x2000000;
> +

Sorry, wrong patch. This cap should be 4M not 32M. I'll send a v2 immediately.

--
Regards,
Chuanhong Guo

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